Research Progress of Single-Atom Catalysts for Electrocatalytic Water Splitting

Abstract

In the context of worldwide energy shortages and environmental degradation, this paper reviews the recent advances of Single-Atom Catalysts (SACs) applied in electrocatalytic water-splitting for hydrogen generation. It discusses the vast application prospects of hydrogen as an eco-friendly energy carrier, and systematically describes the key reactions (hydrogen evolution reaction, HER; oxygen evolution reaction, OER) involved in water electrolysis, as well as their reaction pathways under various electrolyte environments. Furthermore, it analyzes the key challenges including large overpotential and high energy consumption in conventional water electrolysis, and highlights the outstanding energy-saving advantages of the urea oxidation reaction (UOR) as a substitute for the OER process. This work summarizes the excellent catalytic activity of noble-metal-based catalysts, while pointing out their inherent drawbacks such as high cost and scarce reserves. Particular attention is paid to transition-metal-based SACs (Co, Ni, Fe). By summarizing the first-principles and density functional theory (DFT) calculations from previous studies, the hydrogen adsorption Gibbs free energy and catalytic overpotential of both noble-metal and single-atom catalysts are analyzed. We identified Co 1 /g-CN and Nh/g-CN as bifunctional catalysts that exhibit both high-efficiency HER and OER performance, with V 2 /g-CN demonstrating the highest HER activity. Single-atom catalysts, with their high atomic utilization and excellent electrocatalytic activity, provide a theoretical basis for the development of low-cost, highly active water electrolysis catalysts, and are of great significance for advancing the industrial application of water electrolysis for hydrogen production.